Assemblies for creating compound curves in distal catheter regions

ABSTRACT

Compound steering assemblies, usable in both diagnostic and therapeutic applications, enable a physician to swiftly and accurately steer the distal section of the catheter in multiple planes or complex curves to position and maintain ablation and/or mapping electrodes in intimate contact with an interior body surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/054,257, filed Apr. 2, 1998, now U.S. Pat. No. 6,602,278, which is acontinuation of U.S. application Ser. No. 08/645,456, filed May 13,1996, now U.S. Pat. No. 5,820,591.

FIELD OF THE INVENTION

This invention relates to catheters that can by steered by externalcontrols. More particularly the invention relates to such catheters thatcan assume complex three dimensional curves. In addition, the inventionrelates to the use of such complex curves to ablate arrhythmiasubstrates in body tissue.

BACKGROUND OF THE INVENTION

Cardiac mapping is used to locate aberrant electrical pathways andcurrents emanating within the heart. Such aberrant pathways causeirregular contractions of the heart muscle resulting in life-threateningpatterns or disrhythmias.

Ablation of cardiac tissue to create long curvilinear lesions within theheart is also desired for treatment of various disorders such as atrialfibrillation. Various steering mechanisms for catheters carrying suchelectrodes have heretofore been developed and used.

To access various endocardial sites, physicians have used a number ofdifferent catheters and techniques, each of which provides a differentcharacteristic. The use of catheters having limited steeringcharacteristics increases the risk inherent in any catheterizationprocedure and limits the accessibility of many potential ablation sites.

Site access using standard distal tip steerable catheters is less of aproblem because those catheters position a single electrode into contactwith the endocardium and a specific electrode orientation is notrequired. Problems of endocardial site access are accentuated whentrying to simultaneously position multiple electrodes into intimatetissue contact. In this scenario, standard steerable catheterconfigurations orient multiple electrodes in planes emanating about theaxis of the introduction vessel.

A need has thus existed for catheters which, in the nonlinearenvironment found within the heart as well as other body cavities, arecapable of being steered to place ablation elements at a number oflocations while creating intimate tissue contact throughout the lengthof all active ablation elements.

Particularly, a need has existed for a catheter which could effectivelyand accurately form curves in more than one plane for better access ortissue contact. Previous attempts to provide such devices arerepresented by U.S. Pat. No. 5,383,852 wherein there was suggested theuse of steering wire extending from a central lumen of a catheterradially outward to the periphery of a distal end component. Anothersuggestion in represented by U.S. Pat. No. 5,358,479 wherein a singlepull cable is attached to the distal end of a shim which has two flatsections that are twisted relative to each other. This arrangement,however limits the device to bending, first, of the more distal portionof the shim followed by subsequent bending of the more proximal section,thus limiting the procedures using the device.

SUMMARY OF THEN INVENTION

The present inventions provides a catheter, usable in both diagnosticand therapeutic applications, that enables a physician to swiftly andaccurately steer the distal section of the catheter containing theablation and/or mapping element(s) in multiple planes or complex curveswithin the body of a patient. The catheters that embody the inventionallows physicians to better steer a catheter to access variousendocardial sites. In its broadest aspect, the invention providescatheters which enable a physician to position ablation and/or mappingelectrodes inserted within a living body by manipulation of externalcontrols into intimate contact with an interior body surface that curvesin more than one plane.

One aspect of the invention provides a catheter having more than onesteering mechanism for bending the distal section by externalmanipulation into more than one curvilinear direction. Movement of theindividual controls results in bending of the distal section at morethan one location and in more than one direction. Thus the ease ofaccessing and measuring electrical activity in all portions of the heartis increased.

In accordance with another embodiment, the catheter steering assemblymay include a proximal section containing a preformed portion inconjunction with a distal steering mechanism which enables steering in adifferent plane that is non-parallel to the bending plane of thepreformed proximal section, and/or improving tissue contact by movingthe focal point of the steering mechanism to increase the angle ofsteering capable of applying force against the endocardial surface. Thisconfiguration may be accomplished by preforming the proximal section ofthe catheter into the desired curve or manipulating a preformed wire orother support structure which, when freed from the constraints of asheath such as the catheter main body, causes the proximal section toassume the preformed shape.

In accordance with a further embodiment of the invention, a loopcatheter has a preformed proximal end and a moveable wire attached tothe distal end of the spline housing the ablation element(s). Thepreformed proximal end enables the loop to access varying planesrelative to the catheter axis.

Further, objects and advantages of the invention will become apparentfrom the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a catheter having a distal region with acompound steering assembly that embodies features of the invention;

FIG. 2 is a fragmentary side view of the handle portion of the cathetershown in FIG. 1;

FIG. 3 is a perspective view of one embodiment of a compound steeringassembly that embodies features of the invention;

FIG. 4 is a side section view of another embodiment of a compoundsteering assembly that embodies features of the invention;

FIGS. 5A to 5C are side views, with portions broken away and in section,of the compound steering assembly shown in FIG. 4 in use;

FIGS. 6A to 6C are side views, with portions broken away and in section,of an alternative embodiment of a compound steering assembly thatembodies features of the invention being used;

FIG. 7 is an exploded perspective view of a two piece offset springassembly that forms a part of an alternative embodiment of a compoundsteering assembly that embodies feature of the invention;

FIGS. 8 and 9 are side perspective views of the compound steeringassembly that incorporates the two piece offset spring assembly shown inFIG. 7;

FIG. 10A is a side view of another embodiment of a compound steeringassembly that embodies features of the invention;

FIG. 10B is a top sectional view of the compound steering assembly shownin FIG. 10A, taken generally along line 10B—10B in FIG. 10A;

FIG. 11 is a side view of another embodiment of a compound steeringassembly that embodies features of the invention;

FIGS. 12 and 13 are side views of another embodiment of a compoundsteering assembly that embodies features of the invention;

FIGS. 14 and 15 are side views of another embodiment of a compoundsteering assembly that embodies features of the invention;

FIG. 16 is a side view of a complex curve that a compound steeringassembly made in accordance with the invention can assume;

FIGS. 17 and 18 are side views of another embodiment of a compoundsteering assembly that embodies features of the invention;

FIGS. 19A to 19C are side views of another embodiment of a compoundsteering assembly that embodies features of the invention; and

FIG. 20 is block diagram of another embodiment of a compound steeringassembly that embodies features of the inventions.

The invention may be embodied in several forms without departing fromits spirit or essential characteristics. The scope of the invention isdefined in the appended claims, rather than in the specific descriptionpreceding them. All embodiments that fall within the meaning and rangeof equivalency of the claims are therefore intended to be embraced bythe claims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

This Specification discloses electrode-carrying structures that can bebent in compound and complex manners for greater maneuverability withinthe body and enhanced contact with tissue. The illustrated and preferredembodiments discuss these structures, systems, and techniques in thecontext of catheter-based cardiac ablation. That is because thesestructures, systems, and techniques are well suited for use in the fieldof cardiac ablation.

Still, it should be appreciated that the invention is applicable for usein other tissue ablation applications. For example, the various aspectsof the invention have application in procedures for ablating tissue inthe prostrate, brain, gall bladder, uterus, and other regions of thebody, using systems that are not necessarily catheter-based.

FIG. 1 shows a catheter 10, which embodies features of the invention.The catheter 10 includes a handle 12 and a flexible catheter body 14.The distal region 16 of the catheter body 14 carries at least oneelectrode 18. In the illustrated and preferred embodiment, the distalregion 16 carries an array of multiple electrodes 18.

The electrodes 18 can serve to monitor electrical events in hearttissue, or transmit electrical energy to ablate heart tissue, or both.Signal wires (not shown) are electrically coupled to the electrodes 18in conventional fashion. The signal wires extend through the catheterbody 14 into the handle 12. The signal wires electrically connect to anexterior plug 22, which can be connected to signal processing equipmentor a source of electrical ablation energy, or both.

The catheter 10 shown in FIG. 1 includes a steering mechanism 20. Themechanism 20 includes two control knobs 24 and 26 on the handle 12,which can be individually manipulated by the physician.

As will be described in greater detail later, the steering mechanism 20is coupled to a compound steering assembly 28, which is carried withinthe distal region 16 of the catheter body 14. Operation of the controlknobs 24 and 26 bend the steering assembly 28 to flex the distal region16 (as FIG. 1 generally shows) in ways that aid in orienting theablation element 18 in intimate contact with tissue.

FIG. 3 shows one embodiment of a compound steering assembly, designatedby reference numeral 28(1), that embodies features of the invention. Thecompound steering assembly 28(1) includes a spring element formed as asingle piece in two bendable sections 30 and 32. The bendable section 30is distal to the bendable section 32.

In the illustrated embodiment, the bendable sections 30 and 32 arearranged essentially orthogonally relative to each other, being offsetby about 90°. Different offset angles between 0° and 180° may be used.

The proximal end of the proximal bendable section 32 is secured within aguide tube 34. In the illustrated embodiment, the guide tube 34 takesthe form of a coiled stainless steel spring. The guide tube 34 extendsfrom the steering assembly 28(1) rearward within the catheter body 14 tothe handle 12. The guide tube 34 serves to stiffen the catheter body 14and to help impart twisting motion from the handle to the steeringassembly 28(1).

As FIG. 3 shows, a distal steering wire 36 is attached by soldering oradhesive to one surface of the distal bendable section 30. The steeringwire 36 extends from the bendable section 30 through a guide tube 38secured by soldering or adhesive to a surface 40 of the proximalbendable section 32. From there, the steering wire 36 extends throughthe guide tube 34 into the handle 12. The steering wire 36 is coupled tothe control knob 24 within the handle 12, as will be described ingreater detail later.

A proximal steering wire 42 is attached by soldering or adhesive to thesurface 44 of the proximal bendable section 32 opposite to the surface40. From there, the steering wire 42 extends through the guide tube 34into the handle 12. The steering wire 42 is coupled to the control knob26 within the handle 12, as will be described in greater detail.

Flexible heat shrink tubing 56 (shown in FIG. 1 and in phantom lines inFIG. 3) encloses the compound steering assembly 28(1).

As FIG. 2 shows, the control knobs 24 and 26 are individually coupled byshafts, respectively 45 and 46, to rotatable cam wheels, respectively 48and 50, within the handle 12. Rotation of the respective knob 24 and 26serves to rotate its respective cam wheel 48 and 50. The steering wire36 is attached to the cam wheel 48, and the steering wire 42 is attachedto the cam wheel 50.

Further details of the structure of the cam wheels 48 and 50 and theirattachment to the steering wires 36 and 42 are not essential to theinvention and can be found in U.S. Pat. No. 5,254,088, which isincorporated herein by reference.

Rotation of the cam wheel 48 (by manipulation of the knob 24) pulls uponthe distal steering wire 36. This, in turn, pulls upon the distalbendable section 30, flexing the bendable section 30 in the direction ofthe wire 36 (shown by arrow 52 in FIG. 3). The guide tube 38 facilitatesmovement of the steering wire 36 and the transmission of the pullingforce from the cam wheel 48 to the bendable section 30. In the absenceof the pulling force upon the wire 36, the bendable section 30resiliently returns to its normal unbent condition (shown in FIG. 3).

Likewise, rotation of the cam wheel 50 (by manipulation of the knob 26)pulls upon the steering wire 42. This, in turn, pulls upon the proximalbendable section 32, flexing the bendable section 32 in the direction ofthe wire 42 (as arrow 54 shows in FIG. 3). In the absence of the pullingforce upon the wire 42, the bendable section 32 resiliently returns toits normal unbent condition (as FIG. 3 shows).

In the illustrated and preferred embodiment, the guide tube 38 comprisesa stainless steel coil. As a steel coil, the guide tube 38 providesbending resistance and bias for the assembly 28(1) to return to theunbent orientation after deflection.

The compound steering assembly 28(1) makes possible the formation ofcomplex curves in the distal region 16. Pulling on the distal wire 36bends the distal region 16 in the direction 52. Pulling on the proximalsteering wire 42 further bends the distal region 16 in a differentdirection 55.

FIG. 3 shows a single steering wire 36 and 42 attached to each bendablesection 30 and 32 to provide unidirectional bending of each section 30and 32. Of course, either or both bendable sections 30 and 32 mayinclude an opposing pair of steering wires (not shown) to providebidirectional bending action. If bidirectional bending of the distalsection 30 is desired, a guide tube 38 is preferably provided for eachsteering wire attached to the section 30. In this arrangement, the guidetubes should preferably comprise a material at least as flexible as theproximal section 32 itself, so as to not impede the desired bendingaction.

FIG. 4 shows an alternative embodiment of a compound steering assembly,designated 28(2). The compound steering assembly 28(2) includes a springelement formed as a single piece in two bendable sections 58 and 60. Thebendable section 58 is distal to the bendable section 60.

Like the embodiment shown in FIG. 3, the proximal end of the bendablesection 60 is secured within a guide tube 34. Unlike the embodimentshown in FIG. 3, the bendable sections 58 and 60 are not offset fromeach other, but extend in the same plane.

A pair of steering wires 62 and 64 are attached to opposite surfaces ofthe distal bendable section 58. The steering wires 62 and 64 extendrearward through the guide tube 34 within the catheter body 14 forattachment to opposite sides of a rotatable cam wheel (not shown) withinthe handle 12. U.S. Pat. No. 5,254,088 shows the details of thisconstruction, which is incorporated herein by reference. Rotation of thecam wheel in one direction pulls on the steering wire 62 to bend thedistal section 58 in one direction (shown by arrow 66A in FIG. 4).Rotation of the cam wheel in the opposite direction pulls on thesteering wire 64 to bend the distal section 58 in the opposite direction(shown by arrow 66B in FIG. 6). Bi-directional steering of the distalsection 58 is thereby achieved.

The compound steering assembly 28(2) shown in FIG. 4 further includes apreformed wire 68 secured by soldering or adhesive to the proximalbendable section 60. The preformed wire 68 is biased to normally curve.The preformed wire 68 may be made from stainless steel 17/7, nickeltitanium, or other memory elastic material. It may be configured as awire or as a tube with circular, elliptical, or other cross-sectionalgeometry.

The wire 68 normally imparts its curve to the attached bendable section60, thereby normally bending the section 60 in the direction of thecurve. The direction of the normal bend can vary, according to thefunctional characteristics desired. The wire 68 can impart to thesection a bend in the same plane as the distal bendable section 58 (asshown by arrow 66C in FIG. 4), or in a different plane.

In this arrangement, the steering assembly 28(2) further includes a mainbody sheath 70. The sheath 70 slides along the exterior of the catheterbody 14 between a forward position overlying the junction between thewire 68 and proximal bendable section 60 and an aft position away fromthe proximal bendable section 68. In its forward position, the sheath 70retains the proximal bendable section 60 in a straightened configurationagainst the normal bias of the wire 68, as FIG. 4 shows. The sheath 70may include spirally or helically wound fibers to provide enhancedtensile strength to the sheath 70. Upon movement of the sheath 70 to itsaft position, the proximal bendable section 60 yields to the wire 68 andassumes its normally biased bent position. The slidable sheath 70 isattached to a suitable control mechanism on the handle 12.

As FIG. 5A shows, during introduction of the proximal catheter region 16into the body, the sheath 70 is retained in its forward position. Thisretains the proximal bendable section 60 in a substantially straightorientation (as FIG. 4 also shows). After introduction of the distalcatheter region 16 into a desired heart chamber, the sheath 70 iswithdrawn (as shown in a stepwise fashion by FIGS. 5B and 5C). The wire68 urges the proximal bendable section 60 to assume a curvature in thedirection indicated by arrow 66C.

The embodiment of FIGS. 4 and 5A/B/C provides compound curves. Theamount of curvature of the preshaped wire 68 is selected in accordancewith the projected shape of the body chamber into which the catheter isintroduced. Further bending of the distal section 58 is accomplished bypulling on the steering wires 62 and 64.

It should be appreciated that, instead of a stationary preshaped wire 68and movable sheath 70, the steering assembly 28(2) can include aprecurved stylet 72 (see FIGS. 6A to 6C) moveable along the proximalbendable section 60 within a stationary sheath 74. A mechanism (notshown) mounted in the handle affects movement of the stylet 72 under thecontrol of the physician. The stationary sheath 74 extends about thecatheter body 14 up to distal region 16.

When located within the region of the sheath 74 (as FIG. 6A shows), thestylet 72 is retained by the sheath 74 in a straight condition. When thepreshaped stylet 72 is advanced beyond the sheath 74 (as FIGS. 6B and 6Cshow, the stylet 72 imparts its normal curve to the proximal section 60,causing it to assume a curvature determined by the stylet 72.

FIGS. 7 to 9 show another alternative embodiment for a compound steeringassembly, designated 28(3), embodying features of the invention. Thecompound steering assembly 28(3) includes a composite spring 76 formedfrom two individual spring sections 78 and 80 (see FIG. 7). The springsections 78 and 80 include mating central notches 82 and 84, which nestone within the other to assemble the spring sections 78 and 80 together.Soldering or brazing secures the assembled sections 78 and 80 tocomplete the composite spring 76.

The resulting composite spring 76, like the spring shown in FIG. 3,comprises a bendable distal section 30 (spring section 78) and abendable proximal section 32 (spring section 80). The bendable proximalsection 32 is secured to a guide coil in the catheter body in the samemanner shown in FIG. 3.

As FIGS. 8 and 9 further show, the compound steering assembly 28(3)preferably includes two steering wires 86 and 88 attached by solderingor adhesive to opposite surfaces of the distal bendable section 30. Thesteering wires 86 and 88 each extend from the distal bendable section 30through a guide tube 90 secured by soldering or adhesive to one surface92 of the proximal bendable section 32. From there, the steering wires86 and 88 extend through the main guide tube 34 within the catheter body14 into the handle 12 for attachment to a control mechanism in thehandle, as already described.

As FIGS. 8 and 9 also show, the compound steering assembly 28(3)preferably includes one steering wire 94 attached by soldering oradhesive to the proximal bendable section 32 on the surface opposite tothe surface to which the guide tubes 90 are attached. The steering wire94 likewise passes through guide tube 34 within the catheter body 14 forattachment to a second control mechanism in the handle, as alreadydescribed.

As also previously described, the guide tubes 90 preferable take theform of metal coils. As coils, the guide tubes 90 provide increasedspring bias to aid the return of the proximal bendable section 32 to thestraightened position in the absence of pulling force on the steeringwire.

The compound steering assembly 28(3) shown in FIGS. 8 and 9 permitsflexing the distal bendable section 30 in opposite directions normal tothe surface of spring section 78. The compound steering assembly 28(3)also permits independent flexing of the proximal bendable section 32 ina single direction normal to the surface of spring section 80 to whichthe steering wire 94 is attached.

While the illustrated and preferred embodiment of the proximal bendablesection 32 shown in FIGS. 8 and 9 does not permit bidirectional bending,it should be appreciated that two oppositely attached steering wires maybe attached to the proximal section 32 to allow bidirectional steering.In this arrangement, the guide tubes 90 should be made of materials noless flexible than the proximal section itself.

FIGS. 10A and 10B show another alternate embodiment of a compoundingsteering assembly, designated 28(4). The compound steering assembly28(4) includes two separate steering assemblies 96 and 98 radiallyoffset from each other within the catheter body 14 (see FIG. 10B). Eachsteering assembly 96 and 98 includes a bendable spring, respectively 100and 102, carried by relatively small diameter spring coils, respectively104 and 106. The bendable spring 100 extends distally to the bendablespring 102.

A pair of steering wires 108 and 110 are attached to the opposite sidesof the distal steering spring 100 to enable bending in a first plane(shown by arrows 112 in FIG. 10A). A second pair of steering wires 114and 116 are attached to opposite sides of the proximal steering spring102 to enable bending in a second plane (shown by arrows 118 in FIG.10A). As FIG. 10A shows, the small diameter wire coils 104 and 106 maythemselves be contained within the larger diameter steering coil 34within the catheter body 14.

Instead of steering wires 108/110 and 114/116, either or both springs100 and 102 could be attached to preshaped wires (not shown) to assume adesired curvature, to thereby bend the respective spring in the mannershown in FIG. 4. Alternatively, the compound steering assembly 28(4) mayincludes a third, preshaped wire section (not shown), like that shown inFIG. 4 located, either proximally or distally to the bendable springs100 and 102. In these arrangements, an external slidable sleeve (notshown) is used to selectively straighten the preshaped wire whendesired. In this way, complex bends can be formed in the distal regionin at least 3 different planes, or, alternatively, two bending locationscan be provided in a single plane with another bending location beingprovided in an orthogonally separate plane.

FIG. 11 shows an alternative embodiment of a compound steering assembly,designated 28(5), that reduces stiffness of the proximal section. Thecompound steering assembly 28(5) includes two side-to-side guide coils120 and 122. A distal element 124 is soldered between the distal ends ofthe guide coils 120 and 122, thereby collectively forming a distalbendable section 30. A PET retaining sleeve 126 preferably holds theguide coils 120 and 122 together orthogonal to plane of the distalelement 124.

Distal steering wires 128 and 130 are attached to opposite sides of thedistal element 124. The steering wires 128 and 130 pass through theguide coils 120 and 122 and into the main guide coil 34 within thecatheter body 14 for attachment to a control element on the handle. Byapplying tension to a steering wire 128 and 130, the distal element 124and guide coils 120 and 22 bend as a unified structure in the directionof the tensioned steering wire.

A proximal steering wire 132 is soldered to a transverse edge 134 of thedistal element 124. The proximal steering wire 132 also extends into themain guide coil 34 within the catheter body 14 for attachment to anothercontrol element on the handle. By applying tension to the proximalsteering wire 132, the distal element 124 and guide coils 120 and 122bend as a unified structure in a direction orthogonal to the directioncontrolled by the distal steering wires 128 and 130. A second proximalsteering wire (not shown) could be soldered to the opposite transverseedge of the distal element 124 for bidirectional steering.

FIGS. 12 and 13 show another embodiment of a compound steering assembly,designated 28(6) that embodies features of the invention. The steeringassembly 28(6) includes a preformed proximal section 136, whichmaintains a predefined curve, thereby forming a bend in the distalregion 16. The distal end of the preformed proximal section 136 carriesa ferrule 138. The ferrule 138 includes a notch 140. A bendable distalspring 142 fits within the notch 140.

The distal spring 142 includes two oppositely attached steering wires144 and 146. Bi-directional bending of the spring 142 is therebyprovided. Alternatively, a single steering wire could be provided forsingle directional bending.

A sleeve (not shown) made of Kevlar polyester or Kevlar Teflon or plainpolyester preferable encircles the junction of the distal spring 142 andthe ferrule 138 to strengthen the junction. Further details concerningthe sleeve and the attachment of the spring to the distal end of theproximal section are contained in U.S. Pat. No. 5,257,451, which isincorporated herein by reference.

As shown in FIGS. 12 and 13, the notched ferrule 138 holds the distalspring 142 in a plane that is generally orthogonal to the plane of thepreshaped bend of the preformed proximal section 136. The distal spring142 therefore bends in two cross-plane directions, to the right and tothe left of the proximal section 136 (as arrows 148 in FIG. 13 show).Still, it should be appreciated that the notched ferrule 138 can berotated to hold the distal spring 142 in any desired angularrelationship with the preshaped proximal section 136.

For example, FIGS. 14 and 15 show the notch 140 of the ferrule 138 hasbeen rotated to orient the distal spring 142 in generally the same planeas the preformed proximal section 136. In this arrangement, the distalspring 142 is supported for bi-directional, in-plane bending, upward anddownward of the preformed proximal section (as arrows 150 in FIG. 15show).

The proximal section 136 may be preformed into any desired curve, simple(as FIGS. 12 and 13 and FIGS. 14 and 15 show) or complex (as FIG. 16shows, without a distal spring 142 attached).

In the illustrated simple and complex curve embodiments, the proximalsection 136 preferably comprises a braid tube 152 made of polyamide withwire braid, which is thermally formed into the desired shape. Thepreshaped proximal tube 152 preferably contains within it a guide coil154, through which the steering wires 144/146 for the distal spring 142pass. The steering wires 144/146 may also be preshaped like the proximalsection to prevent straightening the preformed proximal section.

In the illustrated and preferred embodiments shown in FIGS. 12 and 13and FIGS. 14 and 15, a flatwire 156 lends additional support to thepreformed proximal section 136. The flatwire 156 is formed in apreshaped curve matching corresponding to the proximal section 136. Theflatwire 156 is preferably bonded to the exterior of the proximal tube152. Also preferably, an exterior polyester shrink tube 158 encloses theflatwire 156 and proximal tube 152 to hold them intimately together. Thepolyester shrink tube 158 can also serve this purpose without firstbonding the flatwire 156 to the proximal tube 152. The assembly of theflatwire 156 and shrink tube 158 as just described can also be used inassociation with the complex curve shown in FIG. 16.

In an alternative embodiment (see FIGS. 17 and 18), a compound steeringassembly, designated 28(7) includes a proximal section 160 comprising aguide coil 166 that does not have a preset curvature. In thisembodiment, the steering assembly 28(7) includes a flatwire 162preshaped into the desired curve. The precurved flatwire 162 includes abracket 164 at its distal end designed to receive and support the guidecoil 166. The bracket 164 is spot welded to the guide coil 166, therebyholding the guide coil 166 in a bent condition corresponding to thecurve of the flatwire 162. A heat shrink polyester tube (not shown)preferably encircles the flatwire 162 and guide coil 166 to hold themtogether. The preformed proximal section 136 is thereby formed.

The compound steering assembly 28(7) includes a notched ferrule 138 likethat shown in the preceding FIGS. 12 to 16. The ferrule 138 is spotwelded to the distal end of the guide coil 166 (see FIG. 18) to receiveand support a distal bendable spring 142 and steering wires 144 and 146,in the manner previously shown in FIGS. 12 to 16. As before described,the notch 140 of the ferrule 138 can be rotated to orient the distalspring 142 in any desired orientation, either orthogonal to the curveaxis of the preformed proximal section (as FIG. 18 and preceding FIGS.12 and 13 show), or in plane with the curve axis of the preformedproximal section (as preceding FIGS. 14 and 15 show), or any desiredangular relationship in between.

Instead of using a preformed braid tube 152 and/or a flatwire 156/162 topreform the proximal section 136 in the manner above described, theproximal section 136 may take the form of a malleable tube, which can bebent by the physician into the desired simple or complex curvature.

As FIG. 16 represents, the preformed proximal section 136 may be shapedin any simple 2-dimensional or complex 3-dimensional shape. Virtuallyany curvature can be selected for the proximal section end, providedthat the curvature permits unimpeded movement of the steering wires144/146 for the bendable distal spring 142. Furthermore, the stiffnessof the preformed proximal section 136 is controlled so that it readilyyields for straightening during introduction, either through thevasculature or a guide sheath.

In vivo experiments demonstrate that the walls of the vasculaturethemselves provide enough force to straighten the proximal section 136made according to the invention, to thereby enable easy advancement ofthe distal region 16 of the catheter body 14 through the vasculature.Guide sheaths may also be used, if desired.

Entry of the distal region 16 of the catheter body 14 into the desiredbody cavity frees the proximal section 136, and it assumes itspredefined shape as previously described. The physician may now furthermanipulate the distal region 16 by rotating the catheter body 14 and/orbending the distal spring 142 to locate the ablation and/or sensingelement(s) 18 at the desired tissue location(s).

The various compound steering assemblies 28(1) to 28(7) that theinvention provides make it possible to locate the ablation and/ormapping electrode(s) at any location within the body cavity. With priorconventional catheter designs, various awkward manipulation techniqueswere required to position the distal region, such as prolapsing thecatheter to form a loop within the atrium, or using anatomical barrierssuch as the atrial appendage or veins to support one end of the catheterwhile manipulating the other end, or torquing the catheter body. Whilethese techniques can still be used in association with the compoundassemblies 28(1) to 28(7), the compound bendable assemblies 28(1) to28(7) significantly simplify placing electrode(s) at the desiredlocation and thereafter maintaining intimate contact between theelectrode(s) and the tissue surface. The compound assemblies 28(1) to28(7) make it possible to obtain better tissue contact and to accesspreviously unobtainable sites, especially when positioning multipleelectrode arrays.

Compound bendable assemblies 28(1) to 28(7) which provide a proximalcurved section orthogonal to the distal steering plane allow thephysician to access sites which are otherwise difficult and oftenimpossible to effectively access with conventional catheterconfigurations, even when using an anatomic barrier as a supportstructure. For example, to place electrodes between the tricuspidannulus and the cristae terminalis perpendicular to the inferior venacava and superior vena cava line, the distal tip of a conventional thecatheter must be lodged in the right ventricle while the catheter istorqued and looped to contact the anterior wall of the right atrium.Compound bendable assemblies 28(1) to 28(7) which can provide a proximalcurved section orthogonal to the distal steering plane greatly simplifypositioning of electrodes in this orientation. Compound bendableassemblies 28(1) to 28(7) which provide a proximal curved sectionorthogonal to the distal steering plane also maintain intimate contactwith tissue in this position, so that therapeutic lesions contiguous inthe subepicardial plane and extending the desired length, superiorlyand/or inferiorly oriented, can be accomplished to organize and helpcure atrial fibrillation.

A transeptal approach will most likely be used to create left atriallesions. In a transeptal approach, an introducing sheath is insertedinto the right atrium through the use of a dilator. Once thedilator/sheath combination is placed near the fossa ovalis underfluoroscopic guidance, a needle is inserted through the dilator and isadvanced through the fossa ovalis. Once the needle has been confirmed toreside in the left atrium by fluoroscopic guidance of radiopaquecontrast material injected through the needle lumen, the dilator/sheathcombination is advanced over the needle and into the left atrium. Atthis point, the dilator is removed leaving the sheath in the leftatrium.

A left atrial lesion proposed to help cure atrial fibrillationoriginates on the roof of the left atrium, bisects the pulmonary veinsleft to right and extends posteriorly to the mitral annulus. Since thelesion described above is perpendicular to the transeptal sheath axis, acatheter which can place the distal steering plane perpendicular to thesheath axis and parallel to the axis of the desired lesion greatlyenhances the ability to accurately place the ablation and/or mappingelement(s) and ensure intimate tissue contact with the element(s). Tocreate such lesions using conventional catheters require a retrogradeprocedure. The catheter is advanced through the femoral artery andaorta, past the aortic valve, into the left ventricle, up through themitral valve, and into the left atrium. This approach orients thecatheter up through the mitral valve. The catheter must then be torquedto orient the steering plane parallel to the stated lesion and itsdistal region must be looped over the roof of the left atrium toposition the ablation and/or mapping element(s) bisecting the left andright pulmonary veins and extending to the mitral annulus. This awkwardtechnique often fails to create adequate tissue contact necessary fortherapeutic lesions.

Preformed guiding sheaths have also been employed to change cathetersteering planes. However, preformed guiding sheaths have been observedto straighten in use, making the resulting angle different than thedesired angle, depending on the stiffness of the catheter. Furthermore,a guiding sheath requires a larger puncture site for a separateintroducing sheath, if the guiding sheath is going to be continuouslyinserted and removed. Additional transeptal punctures increase thelikelihood for complications, such as pericardial effusion andtamponade.

While various preferred embodiments of the invention have been shown forpurposes of illustration it will be understood that those skilled in theart may make modifications thereof without departing from the true scopeof the invention as set forth in the appended claims.

For example, as FIGS. 19A to 19C show a compound loop structure 167carried at the distal end of a catheter body 14. The loop structure 167comprises at least two loop splines 168 and 170.

The loop spline 168 carries an array of ablation elements 172. Accordingto the features of the invention described above, the loop spline 168includes a proximal section 174 that is preformed into a desiredcurvature to access additional planes.

Since the loop spline 168 may be formed from memory elastic materials,the spline 168 may be preformed into any desired shape throughmechanically forming the spline 168 and thermally forming the spline 168in that shape. Preshaped braid tubing or other support may also beincluded to help maintain the shape of the proximal spline bend 174, aspreviously described.

As FIGS. 19B and 19C show, the other spline 170 of the loop structure167 may be retracted or advanced to decrease or increase the loopdiameter to affect desired tissue contact and ablation element location.

The two splines 168 and 170 may be fabricated from a single wire made ofnickel titanium or other memory elastic material. Alternatively, the twosplines 168 and 170 may be fabricated from two or more wires which areconnected by a distal tip at a common point. One spline may be attachedto the catheter body, or two splines may be attached to the catheterbody with another stylet to manipulate the preshaped loop (FIG. 20), orboth splines may be maneuvered.

Various features of the invention are set forth in the following claims.

1. A catheter, comprising: an elongate body including a distal portion,a distal end, a proximal portion, a proximal end, a curved portionhaving a predefined curvature and configured to substantially straightenin response to the application of a force and to return to thepredefined curvature in response to removal of the force, and a controldevice aperture substantially adjacent to the curved portion; a controldevice defining a distal portion secured to the distal portion of theelongate body and extending outwardly therefrom, into the control deviceaperture and proximally to the proximal end of the elongate body; theelongate body distal portion and the control device together defining aloop structure; and at least one operative device supported on thedistal portion of the elongate body.
 2. A catheter as claimed in claim1, wherein the proximal portion defines a longitudinal axis, the loopstructure defines a loop plane, and the loop plane is arranged at anon-zero angle to the longitudinal axis of the proximal portion.
 3. Acatheter as claimed in claim 1, wherein the control device aperture isproximal to the curved portion.
 4. A catheter as claimed in claim 1,wherein the elongate body proximal portion comprises a catheter body. 5.A catheter as claimed in claim 4, wherein the control device aperture isformed in the distal end of the catheter body and the elongate bodydistal portion extends distally from the control device aperture.
 6. Acatheter as claimed in claim 1, wherein the elongate body distal portioncomprises a spline.
 7. A catheter as claimed in claim 1, wherein theelongate body distal portion comprises braid tubing.
 8. A catheter asclaimed in claim 1, wherein the elongate body distal portion includesthe curved portion.
 9. A catheter as claimed in claim 1, wherein thecurved portion defines an approximately ninety degree curvature.
 10. Acatheter as claimed in claim 1, wherein the control device comprises afirst control device, the catheter further comprising: a second controldevice adapted to manipulate the loop structure.
 11. A catheter asclaimed in claim 10, wherein the second control device comprises astylet.
 12. A catheter as claimed in claim 1, wherein the loop structuredefines a diameter and the control device is retractable and advancableto adjust the loop structure diameter.
 13. A catheter as claimed inclaim 1, wherein the control device comprises a spline.
 14. A catheteras claimed in claim 1, wherein the control device is associated with thedistal end of the elongate body.
 15. A catheter as claimed in claim 1,wherein the at least one operative element comprises a plurality ofelectrodes.
 16. A catheter, comprising: an elongate body defining alongitudinal axis and a distal region; a loop associated with the distalregion of the elongate body and defining a loop plane arranged at anon-zero angle to the longitudinal axis of the elongate body; at leastone operative element supported on the loop; and a stylet, which is notused to form the loop, adapted to manipulate the loop.
 17. A catheter asclaimed in claim 16, wherein the loop is fixedly secured to the elongatebody.
 18. A catheter as claimed in claim 16, wherein the non-zero angleis substantially equal to 90 degrees.
 19. A catheter as claimed in claim16, wherein the elongate body includes a pre-set curved portion defininga curvature substantially equal to the non-zero angle.
 20. A catheter asclaimed in claim 19, wherein the non-zero angle is substantially equalto 90 degrees.
 21. A catheter as claimed in claim 16, wherein the atleast one operative element comprises a plurality of electrodes.